The prior art has proposed pressure control devices, for use in a control system of an automatic transmission of an automotive vehicle, and a typical prior art pressure control device is disclosed in U.S. Pat. No. 4,579,145 issued Apr. 1, 1986, with the patentee being Heinz Leiber et al. Said Patent discloses a pressure control device having a housing which encases an electrically energizable field coil and an armature. A spool valve carried within a spool valve housing is movable therein as to control the pressure of a fluid medium passing therethrough. The spool valve is moved in response to a plunger, and the like, positioned by the armature so that the plunger, in effect, acts directly upon the spool valve and the position and motion of the plunger and spool valve are effectively in unison with the armature.
Various problems and difficulties exist in such prior art devices as disclosed by said Patent. For example, only relatively low magnetic forces are available to cause movement of the spool valve resulting in poor response time and presenting a potential fouling. As already indicated, the axial position of the spool valve is always dependent upon the position of the armature which, in turn, requires the hydraulic forces to enter into the armature force balance and allows parasitic forces to be transmitted by the spool valve to the armature and such has a substantial effect on the regulation performed by such prior art devices. Further, it is somewhat difficult, and significantly costly, to manufacture such prior art devices because of the need to maintain precise dimensional relationships, especially axially, between and among the armature, spool valve and the cooperating ports controlled by the spool valve.
The foregoing problems, at least to a great extent, have been overcome by the teachings of U.S. Pat. No. 4,966,195 issued Oct. 30, 1990, with the patentee being Ralph P. McCabe. However, in some respects the pressure regulator assembly of U.S. Pat. No. 4,966,195 still requires significant manufacturing costs as by the use of dual springs at opposite ends of the spool valve and by conveying fluid pressure as from its output or control pressure chamber, to the functional outer-most axial end of the spool valve, as a feed-back pressure.
The invention as herein disclosed and described is primarily directed to the solution of the foregoing as well as other related and attendant problems of the prior art.